Here's a concept of a wall outlet variation. It's size of a wall outlet (occupies the same size standard box in a wall) but instead of mains outlet it has four USB ports for charging various devices.
Now this thing would have to contain a power supply that would convert mains AC into low voltage DC and it would have to support all flavors of protocols for fast charging so that ports are not limited to 0,5 amperes.
The problem is such power supply would dissipate quite a lot of heat (like several watts) as by-product and this heat would need to somehow be dissipated which is rather problematic for a device mount inside wall.
How realistic is this setup in terms of dissipating heat produced by the power supply?